Geant4 Cross Reference |
1 // 1 2 // ******************************************* 3 // * License and Disclaimer 4 // * 5 // * The Geant4 software is copyright of th 6 // * the Geant4 Collaboration. It is provided 7 // * conditions of the Geant4 Software License 8 // * LICENSE and available at http://cern.ch/ 9 // * include a list of copyright holders. 10 // * 11 // * Neither the authors of this software syst 12 // * institutes,nor the agencies providing fin 13 // * work make any representation or warran 14 // * regarding this software system or assum 15 // * use. Please see the license in the file 16 // * for the full disclaimer and the limitatio 17 // * 18 // * This code implementation is the result 19 // * technical work of the GEANT4 collaboratio 20 // * By using, copying, modifying or distri 21 // * any work based on the software) you ag 22 // * use in resulting scientific publicati 23 // * acceptance of all terms of the Geant4 Sof 24 // ******************************************* 25 // 26 // G4EqEMFieldWithSpin implementation 27 // 28 // Created: Chris Gong & Peter Gumplinger, 30. 29 // ------------------------------------------- 30 31 #include "G4EqEMFieldWithSpin.hh" 32 #include "G4ElectroMagneticField.hh" 33 #include "G4ThreeVector.hh" 34 #include "globals.hh" 35 #include "G4PhysicalConstants.hh" 36 #include "G4SystemOfUnits.hh" 37 38 G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4Ele 39 : G4EquationOfMotion( emField ) 40 { 41 } 42 43 G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin() = 44 45 void 46 G4EqEMFieldWithSpin::SetChargeMomentumMass(G4C 47 G4d 48 G4d 49 { 50 charge = particleCharge.GetCharge(); 51 mass = particleMass; 52 magMoment = particleCharge.GetMagneticDipol 53 spin = particleCharge.GetSpin(); 54 55 fElectroMagCof = eplus*charge*c_light ; 56 fMassCof = mass*mass; 57 58 omegac = (eplus/mass)*c_light; 59 60 G4double muB = 0.5*eplus*hbar_Planck/(mass/ 61 62 G4double g_BMT; 63 if ( spin != 0. ) 64 { 65 g_BMT = (std::abs(magMoment)/muB)/spin; 66 } 67 else 68 { 69 g_BMT = 2.; 70 } 71 72 anomaly = (g_BMT - 2.)/2.; 73 74 G4double E = std::sqrt(sqr(MomentumXc)+sqr( 75 beta = MomentumXc/E; 76 gamma = E/mass; 77 } 78 79 void 80 G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G 81 const G 82 G 83 { 84 85 // Components of y: 86 // 0-2 dr/ds, 87 // 3-5 dp/ds - momentum derivatives 88 // 9-11 dSpin/ds = (1/beta) dSpin/dt - s 89 90 // The BMT equation, following J.D.Jackson, 91 // Electrodynamics, Second Edition, 92 // dS/dt = (e/mc) S \cross 93 // [ (g/2-1 +1/\gamma) B 94 // -(g/2-1)\gamma/(\gamma+1) 95 // -(g/2-\gamma/(\gamma+1) \b 96 // where 97 // S = \vec{s}, where S^2 = 1 98 // B = \vec{B} 99 // \beta = \vec{\beta} = \beta \vec{u} with 100 // E = \vec{E} 101 102 G4double pSquared = y[3]*y[3] + y[4]*y[4] + 103 104 G4double Energy = std::sqrt( pSquared + f 105 G4double cof2 = Energy/c_light ; 106 107 G4double pModuleInverse = 1.0/std::sqrt(pS 108 109 G4double inverse_velocity = Energy * pModul 110 111 G4double cof1 = fElectroMagCof*pModuleInver 112 113 dydx[0] = y[3]*pModuleInverse ; 114 dydx[1] = y[4]*pModuleInverse ; 115 dydx[2] = y[5]*pModuleInverse ; 116 117 dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field 118 119 dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field 120 121 dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field 122 123 dydx[6] = dydx[8] = 0.;//not used 124 125 // Lab Time of flight 126 dydx[7] = inverse_velocity; 127 128 G4ThreeVector BField(Field[0],Field[1],Fiel 129 G4ThreeVector EField(Field[3],Field[4],Fiel 130 131 EField /= c_light; 132 133 G4ThreeVector u(y[3], y[4], y[5]); 134 u *= pModuleInverse; 135 136 G4double udb = anomaly*beta*gamma/(1.+gamma 137 G4double ucb = (anomaly+1./gamma)/beta; 138 G4double uce = anomaly + 1./(gamma+1.); 139 140 G4ThreeVector Spin(y[9],y[10],y[11]); 141 142 G4double pcharge; 143 if (charge == 0.) 144 { 145 pcharge = 1.; 146 } 147 else 148 { 149 pcharge = charge; 150 } 151 152 G4ThreeVector dSpin(0.,0.,0.); 153 if (Spin.mag2() != 0.) 154 { 155 dSpin = pcharge*omegac*( ucb*(Spin.cross 156 // from Jackson 157 // -uce*Spin.cross( 158 // but this form ha 159 - uce*(u*(Spin*EField) - 160 } 161 162 dydx[ 9] = dSpin.x(); 163 dydx[10] = dSpin.y(); 164 dydx[11] = dSpin.z(); 165 166 return; 167 } 168